A radar level gauge is commonly used in industry as part of a-guided wave radar (GWR) system to measure the amount (e.g., level) of material (liquid or bulk solid (e.g., powder)) in a tank or a storage tank. A radar gauge provides continuous level (volume) measurement of high reliability at a generally reasonable price. The reliability is obtained due to lack of moving parts and insensitivity of the measurements to changes in process pressure, temperature, and density of measured material. The same applies to an ultrasonic level gauge, but the ultrasonic level gauge generally has a smaller allowable range of pressure and temperature.
The radar gauge for guided or free-space radar is mounted on top of the tank and measures the distance from a reference point, usually a mounting flange at the top of the antenna to the surface of the product material in the tank using reflection of the measuring signal from the surface of the product material. The product level value is obtained by subtracting the measured distance from a total height of the tank. Similarly, the ultrasonic gauge is mounted on top of the tank.
A guided radar gauge, free-space radar gauge or ultrasonic level gauge generally needs to be custom ordered (configured) based specific conditions for a given application, such as application specific maximum temperature, maximum pressure, type of medium, process connection, and tank shape. In the case of a GWR gauge this customization allows for an appropriate choice of sealing, process connection mount, antenna material, and antenna length. Incorrect customization (configuration) at the point of purchase can lead to improper function of the GWR gauge and thus improper function of the measuring system.
Another configuration item is the position the electronic level gauge (ELG) mounted on top of the tank. If there are obstacles in the path of the radar or the ultrasonic signal (measurement signal) between the antenna of the gauge and the surface of the measured material in the tank, measurement may be difficult or impossible. An obstacle is any internal non-product item in the tank or other object in the path of the measurement signal or close to the signal path of the measurement signal. The mounting location should provide an essentially unobstructed path between the antenna of the ELG and the surface of the measured material at each filling level. Particularly in the case of a GWR, there needs to be an unobstructed area around and along the waveguide.
The closest allowable distance between the path of the measurement signal and obstacles in the tank generally depends on the shape of the tank, measured material (i.e., its dielectric constant), maximum material level, and customization of the ELG. Taking into account all of these variables, correct customization, and positioning of the ELG in the tank is generally a challenging task. Moreover, if an already installed ELG needs to be modified or moved to another position on the tank due to unsatisfactory performance, this can lead to significant costs and possible customer′ dissatisfaction.